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At first I was surprised that they don't use edge caching: it seems that all requests get proxied to a backend server, which use just two redis servers as a sha

by atdt 6y ago

At first I was surprised that they don't use edge caching: it seems that all requests get proxied to a backend server, which use just two redis servers as a shared cache. A global internet site can't get good performance this way: RTT between NYC and Sydney is >200ms, so even if your application is lightning fast, it's going to feel slow to users in many parts of the world. Digging around a bit, it seems that they do use Fastly for edge CDN: https://nickcraver.com/blog/2017/05/22/https-on-stack-overflow/ https://nickcraver.com/blog/2017/05/22/https-on-stack-overfl.... Still, it's an impressively lean stack.

EE84M3i 6y ago
Potentially they can't get much edge cache offload for HTML/API content because many people are logged in and/or they do page customization even for non-logged in sessions and pushing logic to the edge isn't worth it.
- atdt 6y ago
  Probably you're right! A webpagetest from Sydney shows pretty dismal performance: https://www.webpagetest.org/result/200801_FJ_dd5f2a76d77bcaaac4ee45d5967ef4e7/ https://www.webpagetest.org/result/200801_FJ_dd5f2a76d77bcaa... ~2 seconds for first contentful paint. That's pretty dismal, IMO, and shows the limitation of their current setup.
  - ksec 6y ago
    >That's pretty dismal, IMO, and shows the limitation of their current setup. Well they cant beat the speed of light. What could they do ?
    - lixtra 6y ago
      Cache their content on different continents and live with only eventual consistency. But as long as there is no competition, why should they complicate things.
  - tenken 6y ago
    A 2 second wait for some impossibly hard IT issue resolution I've been struggling for hours/days against ..... Where do I sign up :D